jade, jadeite, fei cui, Burma, gems

Jadeite may be white, pink, lilac, brown, red, orange, blue, black or many shades of green, and contains different trace elements as colouring agents. Of these trace elements, iron shows the highest concentration and its oxidation states of ferrous or ferric iron produce different colours. In white jadeite nearly all iron is present as ferric (trivalent) iron, while in black jadeite half is ferrous (divalent) and half ferric. In the leaf green jadeites the Fe2+ /Fe3+ ratio ranges from 0.1 to 0.2. The finest green Burmese jadeite, whose colour is caused by up to 0.3 per cent chromium, has been called Imperial jade' or 'emerald jade'. Contents of iron (up to 0.6% Fe) and nickel (0.04% Ni) can modify the rich chromium green of the jadeite. Lilac, mauve or lavender jade may contain manganese (up to 0.01% Mn), cobalt (up to 0.001% Co), chromium (up to 0.001% Cr) and iron (from 0.006 to 0.3% Fe).